This project examines how somatosensory inputs to the primary motor cortex (MI) and somatosensory cortex (SI) influence motor behavior in primates. In particular, the hypothesis that MI neurons respond to mismatches between actual and intended movements was examined by stopping wrist movements in monkeys seeking to make accurate movements. It was found that the response of MI neurons to stopping a movement depends on the distance between the stop position and intended terminal position as well as the joint angle at which the stop occurred. In addition, during unstopped movements some MI neurons responded to the degree to which a movement undershot or overshot the intended target. It is concluded that MI activity reflects the magnitude of the deviation from an intended displacement. This finding provides an important clue concerning the role of peripheral inputs to motor cortex in the initiation and control of movement.